Phase adjuster circuit and phase adjusting method

Abstract

A phase adjustor circuit and a phase adjusting method are capable of preventing a phase shift amount from fluctuating even if a frequency of a transmission carrier wave of a sensor signal fluctuates. A chopping wave converter circuit converts a pulse string signal into a chopping wave. A chopping wave amplitude control circuit compares the amplitude value of the chopping wave with an amplitude reference value and outputs an adjustment signal corresponding to a difference between those values to the chopping wave converter circuit. The chopping wave converter circuit changes a slope of the chopping wave according to the adjustment signal to adjust the amplitude value of the chopping wave. As a result, a feedback group is structured, and the amplitude value of the chopping wave is maintained to a constant value according to the amplitude reference value.

1. A phase adjuster circuit in minute signal amplification using a reference signal and a phase shift reference signal having a given phase difference with respect to the reference signal, comprising:
 a chopping wave converter circuit that converts the reference signal into a chopping wave; 
 a chopping wave amplitude control circuit to which the chopping wave is inputted and which outputs an adjustment signal corresponding to a difference of an amplitude value of the chopping wave with respect to an amplitude reference value to the chopping wave converter circuit; and 
 a phase shift circuit that compares the inputted chopping wave with a given threshold value to output the phase shift reference signal, 
 wherein the chopping wave converter circuit adjusts the amplitude value of the chopping wave according to the adjustment signal, 
 wherein the chopping wave converter circuit comprises: 
 a first constant current source circuit that variably controls the amount of current according to the adjustment signal; 
 a capacitor element that is charged or discharged by the first constant current source circuit; and 
 a switch circuit that controls charge and discharge operation with respect to the capacitor element according to the reference signal, 
 wherein in the case where the amplitude value of the chopping wave crosses the amplitude reference value, the amount of current of the first constant current source circuit is decreased according to the adjustment signal, and 
 wherein in the case where the amplitude value of the chopping wave does not cross the amplitude reference value, the amount of current of the first constant current source circuit is increased according to the adjustment signal. 
 
     
     
       2. The phase adjuster circuit according to  claim 1 , wherein the switch circuit is connected in series with the first constant current source circuit, connected in parallel to the capacitor element, rendered non-conductive at the time of charging the capacitor element, and rendered conductive at the time of discharging the capacitor element. 
     
     
       3. The phase adjuster circuit according to  claim 2 , further comprising a second constant current source circuit that is connected in series with the switch circuit and connected in parallel to the capacitor element. 
     
     
       4. The phase adjuster circuit according to  claim 1 , wherein the chopping wave converter circuit includes at least one edge detector circuit that detects a leading edge of the reference signal and/or a trailing edge of the reference signal, and
 wherein the switch circuit is subjected to conduction control according to the edge detecting operation of the edge detector circuit. 
 
     
     
       5. The phase adjuster circuit according to  claim 4 , further comprising:
 a first chopping wave converter circuit having a first edge detector circuit that detects the leading edge; and 
 a second chopping wave converter circuit having a second edge detector circuit that detects the trailing edge. 
 
     
     
       6. The phase adjuster circuit according to  claim 1 , wherein the phase shift circuit includes a voltage comparator that has a first input terminal to which the threshold value is inputted and a second input terminal to which the chopping wave is inputted. 
     
     
       7. The phase adjuster circuit according to  claim 6 , wherein the chopping wave amplitude control circuit includes an averaging circuit that acquires an average value of the amplitude value of the chopping wave, and
 wherein the average value is inputted to the first input terminal of the voltage comparator. 
 
     
     
       8. A phase adjuster circuit in minute signal amplification using a reference signal and a phase shift reference signal having a given phase difference with respect to the reference signal, comprising:
 a chopping wave converter circuit that converts the reference signal into a chopping wave; 
 a chopping wave amplitude control circuit to which the chopping wave is inputted and which outputs an adjustment signal corresponding to a difference of an amplitude value of the chopping wave with respect to an amplitude reference value to the chopping wave converter circuit; and 
 a phase shift circuit that compares the inputted chopping wave with a given threshold value to output the phase shift reference signal, 
 wherein the chopping wave converter circuit adjusts the amplitude value according to the adjustment signal, wherein the chopping wave amplitude control circuit comprises: 
 at least one monitor circuit that monitors a voltage range of the amplitude value of the chopping wave; and 
 an operational amplifier that is disposed in each of the monitor circuits, has a first input terminal to which an output of the monitor circuit is inputted, has a second input terminal to which the amplitude reference value is inputted, and outputs the adjustment signal. 
 
     
     
       9. The phase adjuster circuit according to  claim 8 , wherein the monitor circuit comprises a peak hold circuit, and the amplitude reference value is an upper limit value of the amplitude value of the chopping wave. 
     
     
       10. The phase adjuster circuit according to  claim 8 , wherein the monitor circuit comprises a bottom hold circuit, and the amplitude reference value is a lower limit value of the amplitude value of the chopping wave. 
     
     
       11. The phase adjuster circuit according to  claim 8 , wherein the monitor circuit comprises an averaging circuit, and the amplitude reference value is an average value of the amplitude value of the chopping wave. 
     
     
       12. The phase adjuster circuit according to  claim 8 , further comprising a holding circuit that holds the output signal of the operational amplifier and then outputs the output signal to the chopping wave converter circuit,
 wherein the chopping wave amplitude control circuit operates at the time of updating the output signal that is held in the holding circuit, and stops at the time of non-updating the output signal. 
 
     
     
       13. The phase adjuster circuit according to  claim 8 , wherein the phase shift circuit includes a voltage comparator that has a first input terminal to which the threshold value is inputted and a second input terminal to which the chopping wave is inputted. 
     
     
       14. The phase adjuster circuit according to  claim 13 , wherein the chopping wave amplitude control circuit includes an averaging circuit that acquires an average value of the amplitude value of the chopping wave, and
 wherein the average value is inputted to the first input terminal of the voltage comparator. 
 
     
     
       15. A phase adjusting method in minute signal amplification using a reference signal and a phase shift reference signal having a given phase difference with respect to the reference signal, comprising:
 converting the reference signal into a chopping wave; 
 acquiring an adjustment signal according to a difference of an amplitude value of the chopping wave with respect to an amplitude reference value; and 
 comparing the inputted chopping wave with a given threshold value to output the phase shift reference signal, 
 wherein the amplitude value of the chopping wave is adjusted according to the adjustment signal when the reference signal is converted into the chopping wave, 
 wherein the phase adjusting method further comprises: 
 controlling variably an amount of current according to the adjustment signal; 
 charging or discharging a capacitor element with current; and 
 controlling a charge and discharge operation with respect to the capacitor element according to the reference signal, 
 wherein, in the case where the amplitude value of the chopping wave crosses the amplitude reference value, the amount of current is decreased according to the adjustment signal, and 
 wherein, in the case where the amplitude value of the chopping wave does not cross the amplitude reference value, the amount of current is increased according to the adjustment signal. 
 
     
     
       16. A phase adjusting method in minute signal amplification using a reference signal and a phase shift reference signal having a given phase difference with respect to the reference signal, comprising:
 converting the reference signal into a chopping wave; 
 acquiring an adjustment signal according to a difference of an amplitude value of the chopping wave with respect to an amplitude reference value; 
 comparing the inputted chopping wave with a given threshold value to output the phase shift reference signal; 
 wherein the amplitude value of the chopping wave is adjusted according to the adjustment signal when the reference signal is converted into the chopping wave, 
 wherein the phase adjusting method further comprises: 
 monitoring a voltage range of the amplitude value of the chopping wave; and 
 outputting the adjustment signal according to an amplification result of the amplitude reference value and the voltage range of the amplitude value.